1. Field of the Invention
The present invention relates generally to dipole antennas.
2. Description of the Related Art
Linearly polarized dipole antennas are commonly used in communication and radar applications. Dipoles can be used individually or as elements in an array antenna. Often a dipole antenna is fed using a microstrip feed line. Microstrip feed lines are utilized in many applications because the devices connected to the dipole are often printed on microstrip boards.
Prior art dipole structures utilized a balanced structure that generally required a balanced-to-unbalanced circuit, also termed a balun circuit, or simply a balun, when fed by a microstrip line. Depending on how the balun circuit was implemented, it had the undesired effect of increasing either the depth or area of the assembly. FIGS. 1A/1B and 2A/2B show instances of prior art dipole antennas utilizing balun circuits. In FIGS. 1A/1B and 2A/2B, the balun circuit is used to split a single input line into a two wire line for connecting to the dipole antenna. FIGS. 1A/1B illustrate how the prior art vertical implementation of a balun circuit increased the depth of the assembly by utilizing area on the vertical ground plane of the assembly. FIGS. 2A/2B illustrate how the prior art horizontal implementation of the balun circuit increased the area of the assembly by utilizing area on the horizontal ground plane of the assembly.